Phylogeny, systematics, and trait evolution of Carex section Glareosae

Abstract

• Premise of the study: The circumboreal Carex section Glareosae comprises 20–25 currently accepted species. High variability in geographic distribution, ecology, cytogenetics, and morphology has led to historical problems both in species delimitation and in circumscribing the limits of the section, which is one of the major tasks facing caricologists today. • Methods: We performed phylogenetic reconstructions based on ETS, ITS, G3PDH, and matK DNA sequences from 204 samples. Concatenation of gene regions in a supermatrix approach to phylogenetic reconstruction was compared to coalescent‐based species‐tree estimation. Ancestral state reconstructions were performed for eight morphological characters to evaluate correspondence between phylogeny and traits used in traditional classification within the section. • Key results: The results confirm the existence of a core Glareosae comprising 23–25 species. Most species constitute exclusive lineages, and relationships among species are highly resolved with both the supermatrix and coalescent‐based species‐tree approaches. We used ancestral state reconstruction to investigate sources of homoplasy underlying traditional taxonomy and species circumscription. We found that even species apparently not constituting exclusive lineages are morphologically homogeneous, raising the question of whether paraphyly of species is a phylogenetic artifact in our study or evidence of widespread homoplasy in characters used to define species. • Conclusions: This study demonstrates the monophyly of Carex section Glareosae and establishes a phylogenetic framework for the section. Homoplasy makes many of morphological characters difficult to apply for taxon delimitation. The strong concordance between supermatrix and species‐tree approaches to phylogenetic reconstructions suggests that even in the face of incongruence among molecular markers, section‐level or species‐level phylogenies in Carex are tractable.

Cryptic Species Due to Hybridization: A Combined Approach to Describe a New Species (Carex: Cyperaceae)

“…is a species endemic to the Iberian Peninsula that belongs to Carex section Glareosae . Previous phylogenetic studies have shown this species to be monophyletic [8]. The highly specific ecological requirements of soils on acid bedrocks and very cool environments [28] explain the distribution of the species in the highest mountains of the Iberian Peninsula, never occurring below 1800 m.a.s.l.…”

“…[6,7]), or focusing on infrageneric taxa (subgenera or sections) (e.g. [8–10]), the restricted geographic coverage of the studies, mostly focused on Europe and North America, and the historical non-natural classifications of the genus, are some of the causes that have hampered an extensive revision of the genus [11]. Moreover, hybridization in Carex has been proposed to limit taxonomic delimitation of species [12–14].…”

“…Species in Carex section Glareosae have experienced multiple taxonomic rearrangements (e.g. [8,19–21]) due to its remarkable morphological, biogeographic and ecological variability [19–21]. The taxonomic identity of some species within the section is still unclear as it occurs with C .…”

“…furva [3,22]. Maguilla et al [8] suggested the existence of an incipient speciation event involving these populations. Morphological data supports the presence of intermediate morphologies in the southern Iberian Peninsula [22] which could reflect hybridization processes between different taxa.…”

“…Hybrids in Carex section Glareosae have been described to be mostly sterile. In fact, hybrid speciation seems not to be a major evolutionary force for Carex in general [12–14] or specifically for this section [8,19,20,26,27]. Previous studies by Maguilla et al [8] and Luceño [22] suggest that hybridization could be avoiding the detection of a cryptic species within C .…”